The present invention relates to a variable-speed power transmission device.
Various types of devices adapted to continuously vary the speed in a transmission of motion are known, among which mention may be made of mechanical, hydrostatic and electric variators.
Among mechanical variators, those in most widespread use are based on the concept of employing the friction torque transmitted by a belt stretched between two pulleys having a fixed center distance and a variable diameter.
The speed change occurs by axially moving the plates of which the pulleys are composed so as to vary the winding diameters of said pulleys.
Hydrostatic variators transform mechanical energy into hydraulic energy with the aid of a pump-motor assembly.
Direct-current motors in which the applied voltage can be varied can be considered electric variators; as is known, the applied voltage is linked to the number of revolutions.
Other kinds of electric variators employ the principles of varying electrostatic and electromagnetic fields.
All these kinds of variators are however characterized by more or less modest results as to the factors of speed, power, torque, weight, dimensions and efficiency.